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Quick Chapter 4

Quick Chapter 4. The Atom!. In the Beginning…. Democritus: Thought everything had little particles. Termed these invisible particles as “atoms” Atomos : “uncut” or “indivisible” Aristotle: Didn’t think this way Gave us four “elements” Earth, Wind, Fire, Water. Oh Johnny Boy.

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Quick Chapter 4

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  1. Quick Chapter 4 The Atom!

  2. In the Beginning… • Democritus: Thought everything had little particles. • Termed these invisible particles as “atoms” • Atomos: “uncut” or “indivisible” • Aristotle: Didn’t think this way • Gave us four “elements” • Earth, Wind, Fire, Water

  3. Oh Johnny Boy • John Dalton: Teacher (Yay!) • Discovered existence of atoms by measuring the masses of elements that form when compounds are made. • Dalton proposed a theory that all matter is made up of atoms, which cannot be divided.

  4. Dalton’s Theory of Atoms (Not all of these are still correct) • All elements are composed of atoms. • All atoms of the same element has the same mass while other elements have different masses. • Compounds contain atoms of more than one element. • Atoms of different elements always combine in the same way.

  5. Double J Thomson • Showed that there are particles in an atom that have a negative charge. • Thomson also showed that atoms are made of smaller particles. • Protons and electrons were thought to be evenly scattered throughout the atom like plum pudding

  6. Rutherford’s Experiment • Ernest Rutherford showed that there is a positively charged center of an atom. • Nucleus: Dense, positively charged mass in the center of the atom.

  7. Rutherford’s Conclusion • By 1920, Rutherford showed the existence of two subatomic particles and predicted a third subatomic particle. • These are protons, electrons, and neutrons.

  8. The Three Subatomic Particles • Protons: Positive particle located in the nucleus • Discovered by Rutherford • Electrons: Negatively charged particle found outside of the nucleus • Discovered by J.J. Thomson • Neutrons: Neutral particle found in the nucleus • Discovered by James Chadwick

  9. 3 Things that separate E,P, and N

  10. Nova Now 12 minutes- CERN • http://www.pbs.org/wgbh/nova/sciencenow/3410/02.html • Cosmic perspective • http://www.pbs.org/wgbh/nova/sciencenow/dispatches/070711.html

  11. Atomic Number and Mass Number • Atomic Number: The number of protons in an element • Identifies an element • Atomic number of an element never changes • Mass Number: Sum total of Neutrons and Protons in a nucleus

  12. How to find number of Neutrons Mass Number - Atomic Number = Number of Neutrons • Example: If an element had an mass number of 12 and an atomic number of 6, how many neutrons does it have? • 12-6 = 6 • What element has an atomic number of 92 and a mass number of 238? • How many neutrons does it have?

  13. Correcting Dalton • Isotopes: Have same atomic number but different mass numbers because of different number of neutrons • Usually are Radioactive too!

  14. Identifying Isotopes • Oxygen with different # of neutrons • Oxygen-16: has 8 neutrons (Standard) • Oxygen-17: has 9 neutrons • Oxygen-18: has 10 neutrons

  15. Bohr’s Model • Niels Bohr: Electrons move in the definite orbits around the nucleus • He studied with Rutherford but focused on electrons rather than the nucleus

  16. I’ve got the power! • Electrons in Bohr’s Model move at a constant speed • Each electron of an atom has a specific amount of energy • Energy levels: Possible energies that electrons in an atom can have • Electrons can move from one energy level to another when the atom gains or loses energy.

  17. Improved Bohr’s Model • He was right about energy levels but wrong about electron movement • Electron cloud: Visual model of the most likely locations for electrons in an atom • More of like a blur with hints at where electrons may be

  18. Orbitals • Orbital: a region of space around the nucleus where an electron is likely to be • Electrons near nucleus has low energy • Electrons away from nucleus has high energy

  19. The chart of orbitals and energy levels • Each orbital can only hold 2 electrons • However each energy level can hold a certain amount of electrons • This is shown in the chart following: Know this chart

  20. The Chart

  21. Configure your Electrons • Electron Configuration: arrangement of electrons in the orbitals of an atom • Ground State: all electrons have the lowest possible energies • If an electron moves toward a level closer to the nucleus it loses energy • Away from the nucleus it gains energy

  22. I’m so excited! • When an atom absorbs enough energy, an electron can move to an orbital with higher energy • Excited State: Electron moved to higher energy orbital and is less stable

  23. Sub-Sub Atomic Particles • Quark-found in the nucleus • A newly hypothesized. subatomic particles • Makes up all other particles in the nucleus • Extremely small

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